narrow: mark the critical chunks of narrowing/widening as unsafe

I'm _mostly_ sure these are the only unsafe chunks here.

Differential Revision: https://phab.mercurial-scm.org/D3718

hgext/narrow/narrowcommands.py

@@ -203,6 +203,7 b' def _narrow(ui, repo, remote, commoninc,'
                               hint=_('use --force-delete-local-changes to '
                                      'ignore'))
 
+    with ui.uninterruptable():
     if revstostrip:
         tostrip = [unfi.changelog.node(r) for r in revstostrip]
         if repo['.'].node() in tostrip:
@@ -269,6 +270,7 b' def _widen(ui, repo, remote, commoninc, '
         repo.setnarrowpats(newincludes, newexcludes)
     repo.setnewnarrowpats = setnewnarrowpats
 
+    with ui.uninterruptable():
     ds = repo.dirstate
     p1, p2 = ds.p1(), ds.p2()
     with ds.parentchange():